German Patent document No. 34 25 609 describes a chuck with a mounting jaw having a fixed connecting shaft. This fixed connecting shaft can be introduced into a corresponding opening in the base jaw and, accordingly, this serves as the plug component of a plug-type connection. The connection can be secured, i.e. closed and locked, by locking elements which are slidingly disposed with the base jaw. The locking elements, in turn, are actuated by a position-control drive or similar actuating means in the chuck body.
With respect to construction considerations, such plug-type connections are cumbersome due to the necessary locking elements. Automated exchange or replacement operations for replacing the mounting jaws cannot readily be achieved. Radial repositioning of the mounting jaws on the base jaws is also precluded although it is normally possible, as described, for the chuck of German Patent document No. 34 25 603.
The chuck described in German Patent document No. 34 25 603 includes a base jaw and a mounting jaw which have cooperating teeth in meshing relationship, with the teeth extending in the direction transverse to the direction of operation, i.e. in the direction of the radially directed shifting of the base jaw. The mounting jaw, accordingly, can be shifted in radial direction by means of the engaging teeth, and along the base jaw.
Automated replacement of jaws in this assembly is achieved by way of a slot in the forwardly directed flank or face of the base jaw in which are also formed the teeth thereof. This slot extends in the direction of movement of the base jaw, and it is open towards the mounting jaw. The adjacent mounting jaw is formed with a guide formation or projection which can be inserted into the mentioned slot of the base jaw so that the mounting jaw can be moved longitudinally and in an interfacing relationship with respect to the base jaw.
At least at one of its operative ends, the guide projection of the mounting jaw is provided with at least one lock shoulder which cooperates with an adjustable and matching lock element including a lock head provided at the base jaw.
The lock head of the lock element can assume a position in which it is disengaged from the guide formation of the mounting jaw, and it can also be moved transversely with respect to the direction in which the base jaw is moved and guided, to be positioned onto the lock shoulder. When the lock head has been positioned it is in contact with the lock shoulder at an interface which is inclined in the direction opposite to the direction of engagement or locking. When moving over and along this inclined interface for being positioned on the lock shoulder, the lock head pulls or advances the guide formation into the slot of the base jaw.
When considered in the direction of adjustment, the lock element is subjected to the force of a lock spring which holds it against the guide projection. A push rod which can be actuated from the exterior of the chuck presses the lock element against the force of the lock spring into the unlocked position.
Even these solutions leave much to be desired, particularly with respect to the configuration of the lock element, with respect to the engagement thereof at the lock retention, as well as with respect to attendant operational requirements.
It is also of detriment in all cases that the securing of the mounting jaw and the base jaw, and tensioning or tightening them is effected solely by a single connecting element, e.g. a lug or guide protection, and this is not sufficient to ensure positive engagement and strong joining of the jaw components. This applies particularly in the case of mounting jaws and base jaws which have large dimensions in the radial direction of the chuck assembly, and/or when these jaw components are to be shifted over relatively long adjustment distances.